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Move insert point after PHI nodes. (#794)
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If replacing a PHI node with another instruction, make sure the
insertion point is after the last PHI node in that block. This prevents
the assertion described in #779.
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zoecarver committed Oct 16, 2020
1 parent 241cadd commit 5d659bd
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11 changes: 11 additions & 0 deletions lib/Codegen/Codegen.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -99,6 +99,17 @@ llvm::Value *Codegen::getValue(Inst *I) {
if (!V0)
return nullptr;

// PHI nodes must be the first instructions in a basic block. If we're
// replacing a PHI node with another instruction, make sure it comes after the
// other PHI nodes.
if (ReplacedInst &&
isa<PHINode>(ReplacedInst->getNextNode())) {
Instruction *InsertPoint = ReplacedInst;
while (isa<PHINode>(InsertPoint))
InsertPoint = InsertPoint->getNextNode();
Builder.SetInsertPoint(InsertPoint->getNextNode());
}

switch (Ops.size()) {
case 1: {
switch (I->K) {
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46 changes: 46 additions & 0 deletions test/Pass/insert-after-phis.ll
Original file line number Diff line number Diff line change
@@ -0,0 +1,46 @@
; RUN: %opt -load %pass -souper -S -stats -o - %s 2>&1 | %FileCheck %s

; The main thing being tested here is just that the verifier doesn't error
; because a PHI node comes after another instruction.

@c = local_unnamed_addr global i32 0, align 4
@d = local_unnamed_addr global i32 0, align 4
@e = local_unnamed_addr global i64 0, align 8
@b = local_unnamed_addr global i32 0, align 4
@a = global [1 x i32] zeroinitializer, align 4
@f = global [1 x i32] zeroinitializer, align 4

; CHECK: define void @g()
define void @g() {
entry:
br i1 icmp ule (i32* getelementptr inbounds ([1 x i32], [1 x i32]* @a, i64 0, i64 0), i32* inttoptr (i64 6 to i32*)), label %for.body.lr.ph, label %for.end14

for.body.lr.ph:
%b.promoted = load i32, i32* @b, align 4
%e.promoted = load i64, i64* @e, align 8
br label %for.inc10

for.inc10:
%0 = sub nuw nsw i32 1, %b.promoted
%cmp = icmp sge i32 %b.promoted, 0
br i1 %cmp, label %for.inc10, label %for.inc13

for.inc13:
%.lcssa = phi i32 [ %0, %for.inc10 ]
%dec.6.lcssa = phi i64 [ %e.promoted, %for.inc10 ]
%inc = add nsw i32 %b.promoted, 1
br i1 icmp ule (i32* getelementptr inbounds ([1 x i32], [1 x i32]* @a, i64 0, i64 0), i32* inttoptr (i64 6 to i32*)), label %for.inc10, label %for.cond.for.end14_crit_edge

for.cond.for.end14_crit_edge:
%.lcssa.lcssa = phi i32 [ %.lcssa, %for.inc13 ]
%dec.6.lcssa.lcssa = phi i64 [ %dec.6.lcssa, %for.inc13 ]
%inc.lcssa = phi i32 [ %inc, %for.inc13 ]
store i64 %dec.6.lcssa.lcssa, i64* @e, align 8
br label %for.end14

for.end14:
ret void
}

; CHECK: - Number of insts removed

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